November 2018

Presentation spotlightWide-angle IOL: an option for AMD patients with cataract

by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer

Intraocular telescopes for AMD patients with description of the working principle and examples of the typical magnification achieved
Source: Pablo Artal, PhD

Not only is cataract surgery beneficial for vision in patients with macular diseases, but the choice of the right implant can provide an added visual advantage

Improving vision in patients with age-related macular degeneration is an arduous, often disappointing task. The irreparable damage to the retina caused by AMD precludes the restoration of the sharp visual acuity provided by the central fovea and calls for inventive solutions that implement the still healthy yet more peripheral retinal tissues. A novel IOL idea seems to be offering encouraging visual outcomes in AMD patients with concomitant cataract, according to a presentation on this topic at the 22nd ESCRS Winter Meeting.
A Spanish research team has investigated a new approach to improving vision in patients with macular diseases. According to a presentation given by Pablo Artal, PhD, Laboratorio de Optica, Universidad de Murcia (LOUM), Spain, implanting standard lenses after cataract surgery offers these patients very limited visual benefits. “When you are doing standard cataract surgery in AMD patients, the benefit achieved is modest with standard lenses. There are some reports in the literature that show no more than a six-letter improvement,” Dr. Artal said. “Cataracts diffuse the light entering the eye and increase ocular scatter severely, which reduces contrast of the retinal image. The degree of contrast sensitivity that is lost largely depends on the type of cataract. If you look at the central foveal visual acuity in eyes with different degrees of cataract and a healthy macula, you see a good recovery of visual acuity after surgery. In an AMD patient, however, cataract surgery does not improve visual acuity the same way. Since AMD impacts the central fovea, the effect of cataract and consequently the effect of scatter on vision is much higher.”

Cataract investigations at LOUM

AMD is a progressive disease that damages the central fovea, the area with the highest density of photoreceptors. Individuals affected by AMD become reliant on the use of the peripheral, healthy areas of the retina that give lower image resolution. Dr. Artal explained that the central fovea provides visual acuity of 1 logMAR (20/20), while the retinal areas that are 5 degrees outside of the fovea give a visual acuity of 0.3 logMAR, and the retinal areas 10 degrees outside of the fovea give a visual acuity of 0.15 logMAR. He elucidated, “Five degrees is not much. Holding your thumb up with your arm stretched out in front of your face represents about 1.5 degrees beyond the central fovea, and 5 degrees is represented by about three finger widths. This roughly allows you to understand how much vision you lose within just a few small degrees beyond the fovea.”
Dr. Artal and his team at LOUM constructed a cataract simulator in their laboratory with which they could realistically induce cataract in a subject. By creating scenarios with different types of cataract and different degrees of scatter, they were able to better understand how scatter affected visual acuity in the retinal periphery in eyes with different types of cataract. They saw that scatter (i.e., cataracts) in non-AMD affected eyes could reduce visual acuity in the fovea from –0.1 to 0.4 logMAR. The same amount of scatter (cataract) affected the visual acuity in the periphery of eyes with AMD from 0.8 to 0.95 logMAR.

Experimenting with a wide-angle IOL option

According to the research team’s recent study using wide-angle IOLs in AMD patients, visual acuity was better than that achieved using standard implants.1 “This IOL may be the next viable approach to help AMD patients magnify objects to improve visual acuity,” Dr. Artal said. “You need to target your patients for hyperopia using a novel, wide-angle IOL. Then, using external spectacles, a telescopic effect is achieved together with the internal lens implant. You get a modest type of magnification. The +3 D implant gives a magnification of 1.11 times, with spectacles, and a +6 D implant gives a magnification of 1.19 times. Unlike healthy patients, AMD patients have no problem with spectacles. They are used to them. This approach may be a good option in some patients with AMD,” he said.
The study included 244 eyes with dry/stable wet AMD with >0.3 logMAR visual acuity that were implanted with the iolAMD Eyemax mono (London Eye Hospital Pharma, London, U.K.). The iolAMD is a single-piece, injectable, hydrophobic acrylic IOL for implantation in the capsular bag that offers an optimized retinal image to all macular areas within 10 degrees of retinal eccentricity. The microincision telescopic lens maintains the safety profile of routine cataract surgery, as opposed to previous, much larger telescopic lenses. The mean patient age in the study was 80 years and the mean follow-up time was 3 months (range: 1–16 months).
No eye had worse corrected distance visual acuity (CDVA), and the frequency of perioperative complications was equivalent to that seen with standard IOL implantation. The postop refractive outcomes were within ±1 D of the target refraction in 88% of cases. The mean preoperative CDVA for 4 meters distance improved from 1.06 logMAR to 0.71 logMAR postoperatively (p<.0001), which was the equivalent of an 18-letter improvement, according to the Early Treatment Diabetic Retinopathy Study. The mean preoperative corrected near visual acuity (CNVA) for 33 centimeters distance improved from 1.36 logMAR to 0.88 logMAR postoperatively (p<.0001).
“The wide-angle design of the implant is effective in controlling peripheral blur in eyes with macular disease. We have done several studies using this novel IOL and the gain in letters for distance is roughly double of that achieved through the implantation of standard IOLs in these patients,” Dr. Artal said. “My own experience with a small group of 15 patients was that this IOL received positive feedback from patients, however, the patients were selected for implantation and were in early stages of AMD, with baseline visual acuity of no lower than 0.3/0.4 logMAR. Patients with lower visual acuities have even higher expectations, and although this device is useful, it does not perform miracles.”
Dr. Artal observed that outcomes using this IOL or any telescopic, magnifying device were largely dependent on the degree of AMD and that it was important for AMD patients to understand their own expectations. “Cataract surgery with standard IOL provides a modest benefit, and it is important to remember that surgeons should avoid the implantation of diffractive lenses if they opt for standard IOLs because they reduce contrast. Other options include large, telescopic implants that require special, more complicated surgeries, which should be reserved for advanced AMD cases. When the visual field is reduced, you need to balance that with the benefits of magnifying IOLs because magnifying IOLs reduce the field of vision. Finally, AMD patients should understand that when you are doing any type of cataract surgery, you are helping them, but in a way, they are buying time. The macular disease will progress, and doing a cataract intervention is not curing the retinal disease. Many patients are not going to understand this. The iolAMD is a promising area. I think there are going to be more innovations like this coming in the future.”